JP3844429B2 - Scanning radar equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scanning radar apparatus that determines the lateral position of a target based on the intensity of a reflected wave when scanning the direction of emission of radio waves, and in particular, together with the distance to the target and the relative speed for controlling the inter-vehicle distance. The present invention relates to a scanning radar apparatus that measures a lateral position of a target.
[0002]
[Prior art]
If the FM-CW radar is used, the distance to the target existing in front of the host vehicle and the relative speed of the target can be measured. Based on these measured values, for example, in order to appropriately control the inter-vehicle distance from the vehicle traveling ahead, it is necessary to determine the lateral position of the target existing ahead.
[0003]
In the scanning radar apparatus, as shown in FIG. 1B, the direction of emission of radio waves is scanned, the direction in which the intensity of the reflected wave from the target is maximum is set as the target direction, and then the lateral position of the target Is determined.
According to this method, if there is no deviation between the direction of viewing the target from the vehicle (direction to the target) and the direction of movement of the target (direction of the target), the lateral position of the target is accurately determined. Can do.
[0004]
[Problems to be solved by the invention]
However, if there is a difference between the direction to the target and the direction of the target, the lateral position of the target cannot be accurately determined. For example, in the case shown in FIG. 1A or FIG. 1C, the power of the reflected wave is maximized at one end of the target, and the lateral position cannot be estimated accurately.
[0005]
Accordingly, an object of the present invention is to provide a scanning radar apparatus that can accurately determine the lateral position of a target even when the direction of the target is deviated from the direction toward the target.
[0006]
[Means for Solving the Problems]
According to the present invention, the lateral position determining means for determining the lateral position X of the target based on the intensity of the reflected wave from the target when the radio wave emission direction is scanned, and the direction to the target and the direction of the target There is provided a scanning radar apparatus comprising: means for determining an angle ψ formed by: means for determining a lateral position correction value ΔX based on the angle ψ; and means for correcting the lateral position X with the correction value ΔX. .
[0007]
The angle ψ determining means is based on the formula ψ = θ−tan ⁻¹ {dcos θ / (R−) based on the radius of rotation R, the distance d from the target, and the angle θ formed by the direction to the target and the direction of the host vehicle. dsin θ)}
The angle ψ is preferably determined by
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows the configuration of an in-vehicle scanning millimeter wave radar apparatus as an embodiment of the scanning radar apparatus of the present invention.
In FIG. 2, the ECU 10 calculates the turning radius R of the own vehicle based on the signal from the yaw rate sensor 12 and the signal from the vehicle speed sensor 14, and sends it to the FM-CW radar 16 together with the vehicle speed data. The radius of rotation R can also be calculated using data from the steering sensor instead of the data of the yaw rate sensor 12. The FM-CW radar 16 emits a millimeter-wave band radio wave that is frequency-modulated with a triangular wave to the front of the host vehicle, analyzes the reflected wave, and thereby the distance from the target existing ahead and the relative velocity of the target. Is calculated. Further, as described above, the FM-CW radar 16 scans the emission direction of the radio wave, and calculates the estimated value X [m] of the lateral position of the target based on the power distribution of the reflected wave at that time. Further, the lateral position correction value ΔX is calculated based on the rotational radius R data from the ECU 10, and the lateral position X corrected thereby is sent to the ECU 10 together with the distance and relative speed data. Based on these data, the ECU 10 generates and outputs a control signal for maintaining a constant distance from the vehicle traveling ahead.
[0009]
3 and 4 show the principle of the method for calculating the correction value ΔX of the lateral position X in the present invention. 3 and 4, R is a radius of rotation of the host vehicle 20, d is a distance from the target 22, ψ is a direction of viewing the target 22 from the host vehicle 20 (direction to the target), and a traveling direction of the target 22. The angle formed by (the direction of the target), φ represents the angle formed by the direction of the host vehicle 20 and the direction of the target 22.
As is clear from FIG. 4, the angle φ is φ = tan ⁻¹ {dcos θ / (R−dsin θ)}.
Can be calculated. Therefore, the angle ψ is ψ = θ−φ
It can be calculated from Since this angle ψ represents the deviation between the direction of radio wave irradiation to the target and the direction of the target, for example, the correction value ΔX is determined from a linear relationship passing through the origin as shown in FIG. Then, the lateral position X is set to X = X + ΔX by the determined ΔX.
Correct as follows. These arithmetic processes are realized by software, for example, by incorporating a CPU in the FM-CW radar 16.
[0010]
In the relationship of FIG. 5, as ψ increases, ΔX increases accordingly. However, as shown in FIG. 6, there is an upper limit on the absolute value of ΔX because there is a limit to the width of a realistic car. It is desirable to Further, since it is not preferable that the lateral position X fluctuates due to noise in a range where the value of ψ is small, it is desirable to provide a dead zone for maintaining ΔX at 0 around the angle 0 as shown in FIG. When the distance to the target is large, the correction amount ΔX should be small, so it is better to make ΔX small in order to avoid the influence of noise. In this case, when the distance d increases as shown in FIG. 8 or FIG. Similarly, when the rotation radius R is large, the correction coefficient is reduced to avoid the influence of noise.
[0011]
Since the calculated ΔX includes noise, for example, ΔX _n = (ΔX _n−1 × 3 + ΔX) / 4 rather than correcting X by using it as it is.
It is desirable to reduce the influence of noise by using ΔX _n calculated in (1). Further, when it is determined that the target is traveling in the lane in which the host vehicle is traveling based on the uncorrected lateral position X, ΔX is multiplied by, for example, 0.7 to reduce the correction amount. When the amount of change of the rotation radius R in the unit time by the driver's steering operation is larger than a predetermined value, it is not preferable to correct X by following it, so the correction amount ΔX is set to zero. Further, the lateral position is not corrected for the object that is determined to be a stationary object. The neutral position is learned to cancel the drift of the steering sensor (or yaw rate sensor) that is the origin of the turning radius R, but the lateral position X is not corrected until this is completed.
[0012]
The calculation of the correction value ΔX has been described above. However, even if a ΔX value other than 0 is calculated depending on the target, if it is found that the correction of the horizontal position is unnecessary from another point, the correction of the horizontal position is performed. It is desirable not to perform.
That is, for a target that meets any of the following conditions (1) to (4), even if a ΔX value that is not 0 is calculated, it is considered that there is no need for correction, and thus correction is not performed. .
(1) A target that is determined to be traveling in the range of the lane in which the vehicle is traveling according to the lateral position X before correction.
(2) A target whose power (peak intensity) is below a predetermined fixed reference value or reference value as a function of distance. This is because a small target, for example, a two-wheeled vehicle, rarely distributes reflected waves (peaks) in the angular direction.
(3) A target in which there is no distribution of reflected waves (peaks) in the angular direction and peaks due to reflected waves appear only in one direction.
(4) It is judged that there are a plurality of reflection points physically like a large truck, and a process of taking the average of the angles of a plurality of reflected waves (peaks) whose distance, angle, and relative velocity are approximated was performed. Target. The reason is that the angle has already been corrected by the process of taking the average, and further correction will result in overcorrection.
For a target that has been corrected in the past even if it does not fall under any of the above (1) to (4), this is regarded as a target that generates an angular deviation. Even if it falls under any of (4) to (4), it is desirable to always make it a correction target.
[0013]
【The invention's effect】
As described above, according to the present invention, there is provided a scanning radar apparatus that can accurately determine the lateral position of a target regardless of the direction of the target.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining problems in lateral position determination.
FIG. 2 is a block diagram showing a configuration of an in-vehicle radar device according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a method for calculating an angle ψ.
FIG. 4 is a diagram illustrating a method for calculating an angle ψ.
FIG. 5 is a graph for explaining calculation of a correction value ΔX from an angle ψ.
FIG. 6 is a graph showing a second example of calculation of a correction value ΔX from an angle ψ.
FIG. 7 is a graph showing a third example of calculation of a correction value ΔX from an angle ψ.
FIG. 8 is a diagram illustrating a first example of correction of ΔX according to distance d or rotation radius R;
FIG. 9 is a diagram illustrating a second example of correction of ΔX according to the distance d or the rotation radius R;

Claims (13)

Lateral position determining means for determining the lateral position X of the target based on the intensity of the reflected wave from the target when the emission direction of the radio wave is scanned;
Means for determining an angle ψ between the direction to the target and the direction of the target;
Means for determining a lateral position correction value ΔX based on the angle ψ;
A scanning radar apparatus comprising: means for correcting the lateral position X with a correction value ΔX. The angle ψ determining means is based on the formula ψ = θ−tan ⁻¹ {dcos θ / (R−) based on the radius of rotation R, the distance d from the target, and the angle θ formed by the direction to the target and the direction of the host vehicle. dsin θ)}
The scanning radar apparatus according to claim 1, wherein the angle ψ is determined by. 3. The scanning radar apparatus according to claim 1, wherein the correction value determining means determines the correction value ΔX in such a manner that the correction value ΔX has an upper limit value and a lower limit value. The scanning type according to any one of claims 1 to 3, wherein the correction value determining means determines the correction value ΔX in a form having a dead zone in which the correction value ΔX does not change even if the angle ψ changes within a range including 0. Radar device. 5. The correction value determining means according to claim 1, wherein when the distance d to the target is large, a value smaller than the correction value when the distance to the target is small is set as a correction value ΔX. Scanning radar device. 6. The scanning radar apparatus according to claim 1, wherein when the rotation radius R is large, the correction value determination unit sets a value smaller than a correction value when the rotation radius is small as a correction value ΔX. The correction value determining means, when it is determined that the target is traveling in the lane in which the host vehicle is traveling, sets a value smaller than the determined ΔX as the correction value ΔX. The scanning radar device according to any one of the preceding claims. The scanning radar according to any one of claims 1 to 7, wherein the correction value determining means sets the correction value ΔX to 0 when the amount of change in the rotation radius R within a unit time is larger than a predetermined value. apparatus. It further comprises target judging means for judging whether or not the lateral position correction is necessary for each target.
9. The horizontal position correction unit according to claim 1, wherein the horizontal position correction unit does not perform horizontal position correction on a target determined by the target determination unit as not requiring horizontal position correction regardless of the correction value ΔX. Scanning radar device. 10. The scanning radar apparatus according to claim 9, wherein the lateral position correcting means always corrects the lateral position for a target that has been determined to require lateral position correction in the past. The scanning type according to claim 9 or 10, wherein the target determination means does not require horizontal position correction for a target that is determined to be traveling in a lane in which the host vehicle travels according to the lateral position X before correction. Radar device. The scanning radar apparatus according to any one of claims 9 to 11, wherein the target determination unit makes a lateral position correction unnecessary for a target determined to have substantially no angular direction distribution. The scanning radar apparatus according to any one of claims 9 to 12, wherein the target determination unit makes a lateral position correction unnecessary for a target obtained by averaging angles of a plurality of reflections.

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